1. Field of the Invention
This invention is in the field of manufacturing apparatus and, more particularly, relates to a transport system for transporting fixtures adapted to hold a workpiece from one station to another station. The mechanism for moving the fixtures is a fixture guide rail which is provided with a chain guide recess through which a continuous loop of a cable chain can be caused to move. The chain is provided with drive pins which project from one side of the chain and which drive pins engage a fixture to move the fixture from the one station to the other along the guide rail. The spacing between drive pins is substantially uniform and greater than the corresponding dimensions of the fixture.
2. Description of the Prior Art
The development of integrated circuit (IC) chips, particularly medium and large scale IC chips, has created a need for improved manufacturing processes which lend themselves to automating the connecting of the conductive leads of a lead frame on which an IC chip is bonded to substrates when the IC chips are interconnected to form useful electronic circuits. In implementing such processes, fixtures such as those described and illustrated in U.S. Pat. No. 4,069,496, which issued on Jan. 17, 1978, can be used to removably hold a segment of a film strip on which an IC chip has been bonded to a lead frame, which frame is, in turn, attached to the segment.
In automating the process of manufacturing hybrid substrates, a plurality of fixtures is assembled, or collected, in a magazine, such as that described and illustrated in application Ser. No. 153,367, filed May 27, 1980, entitled "Material Handling Apparatus", which application is assigned to the same assignee as this application. Each of the fixtures stored in a magazine, such as that disclosed in application Ser. No. 153,367, filed May 27, 1980, may have as its workpiece an IC chip bonded to a segment of film held by each fixture. Each such magazine has the capacity of having such fixtures inserted into the magazine and subsequently removed as steps in the process of manufacturing electronic circuits.
U.S. Pat. No. 4,068,767, which issued on Jan. 17, 1978, is the closest relevant prior art known to applicant. This patent teaches a transfer mechanism which withdraws a fixture from the bottom of a stack of such fixtures in a transferor magazine and inserts, or loads, the fixtures serially into the bottom of a stack of such fixtures into a second, or transferee, magazine. The transport system for such a mechanism includes a pneumatically powered linear actuator.
There is a need for an improved transport mechanism which need not be lubricated so that it is adaptable for use in a clean environment, i.e., in a clean room, such as that in which semiconductor devices are produced or in which hybrid circuits are fabricated. There is also a need for a transport mechanism which is able to move fixtures sequentially and with precision from a transferor station in a transferor base to a transferee station in a transferee base and which is able to position the fixtures along the route at work stations located between the transferor and transferee stations so that various manufacturing steps can be performed on the workpiece carried by each fixture. One problem with the use of prior art linear actuators is that it is only possible to move a fixture from one place to another place in one step or to incrementally move the fixtures along the fixture guide rail in steps substantially equal to the dimension of the fixtures in the direction of movement with one fixture in contact with the other between the initial and last stations.